It's a free Killing Floor weekend on Steam, as Tripwire celebrates the release of the free Level Up content pack, adding new creatures, classes, weapons, maps, and perk levels to the co-op mutant survivor game.

Killing Floor is incredibly fun, and now it's even more so. The free Level Up content pack punctuates Tripwire Interactive's dedication to providing lasting value to their fans, keeping the game fresh with a healthy injection of new content. There are three new maps, including one set during the aftermath of a Halloween rave in an abandoned lunatic asylum, which would probably be more enjoyable if you arrived while the rave was going on. They're introducing The Husk, a new specimen with a fireball launcher grafted to its arm, which sounds uncomfortable, along with a demolitions perk for those who like blowing up the crazed mutants. All perks now have an additional level, hence the Level Up moniker, and several new weapons are introduced, including a medic gun that shoots healing darts from afar.

All of this new content is free to everyone who has purchased the game, as well as those who take part in the free Steam weekend, going on until Sunday. As an added bonus, those who opt to purchase the full game this weekend get it for 25% the normal price. $14.99 for Killing Floor is an absolute steal.

New Features in the Level Up Pack:
* KF-Wyre: a map set in the dark forests in southern England, with a hidden Horzine facility buried underground.
* KF-Bedlam: this map is set in the aftermath of a Halloween rave at a crumbling and abandoned lunatic asylum, forcing your squad to fight through claustrophobic corridors and haunted hallways, all to the left-over rave tunes and lighting.
* KF-Waterworks: the winning map from Wave 1 of the Grindhouse mapping contest, Waterworks' stunning visuals and gameplay blew the judges away. Now you have to blow away all the specimens from the ruins of the pumping station.
* New Demolitions Perk: this one is for all those who like to blow stuff up. This is the guy who knows his explosives. Proximity-fuzed pipe-bombs and grenade launchers – you get the idea!
* All Perks now have a Level 6 to achieve – with even more goodies for getting there.
* Introducing our new Specimen – the Husk: this was Horzine's first serious attempt at a clone with a ranged attack. Grafting a fireball-launcher to his arm gave him a vicious long-range attack and gives the gameplay a whole new dynamic. Just don't stand still when he arrives – and have a Sharpshooter handy to keep him at bay.
* MP7M Medic Gun: Horzine took a submachine gun and added their prototype healing-dart gun to it. Now the Medic has the perfect combo of fire-power combined with the ability to heal team-mates from a distance.
* The M79 Grenade Launcher has been tucked away in Army arsenals for decades. It may be old, but it is ever-reliable and still packs quite a punch.
* The M32 Multiple Grenade Launcher takes the basic grenade launcher and allows you to fire multiple rounds in quick succession, for even more "boom".
* AA-12 Auto Shotgun: a prototype every Support Specialist wants to get his hands on. Devastating firepower, but just eats ammo!
* M14 Enhanced Battle Rifle: the EBR is a Special Forces version of an old favorite, just right for all the Sharpshooters amongst us.
* SCAR Mk17: another Special Forces weapon, featuring a good rate of fire, good accuracy and a good heavy round. Just what every serious Commando wants!
* Proximity-fused Pipe-bomb: an all-time favorite of Demolitions guys the world over. Arm it, drop it and wait for a horde of bad guys to run over it. Just don't be there when they do!
* Game Lobby Movie Trailers – short movie trailers will now play during the game lobby before a match. These ads will help keep the free content packs rolling!